Trying to copy sell to other sheet and retaining the value when original cell is edited.

Hi!

I'm having a problem with my sales tracking excel.
I have Daily sheet with different products I sell, then I have another sheet for monthly tracking.

So, I have Product A in daily sheet, and same cell in Monthly sheet. Now i'm trying to get that excel work to fill automatically all sales to monthly sheet without removing data when i reset my daily sheet.

Example:

I sell product A -> I mark it in my daily sheet. Now i have this one in Daily sheet marked, and in monthly sheet (i use =Sheet1!xx), it wored as i wanted, my sell moved to other sheet as well. But the problem comes when i reset values from Daily sheet and poof , monthly sheet is empty too (ofcourse because that command just copies the other cell).

So I'm wondering is it possible to get it work this way:
1.1 I sell 15 product a , I mark them to daily sheet and monthly sheet shows that 15 too.
2.1 I reset daily sheet in the morning when start new working day so Product a sell is 0 in that sheet, but in monthly sheet there is still that 15. And during the 2.1 I sell 25 product A , so that amount is in the daily sheet but monthly shows 40.
and etc..

I have been searching help to this for hours but i didn't find anything.

Hopefully someone in here understand what i'm looking for and is able to help me!

Thanks!